Underlying the development of bimanual phaco is the reduction in incision size to below 1.5 mm. Therefore, new instrumentation adapted to this new constraint is necessary to ensure the safety and ease of application of the new technique. Many of the detractors of this technique have tried it with inappropriate instruments resulting in failure and therefore rejection of the technique on their part.
A number of companies have developed the instruments that are essential for safe operations such as knives, capsulorhexis forceps, irrigating choppers, irrigating manipulators and aspiration probes specially designed for bimanual phaco. In this work, I will provide a partial overview of each as I have experienced them in use.
For the incision
The first problem in beginning with bimanual phaco is the creation of two self-sealing corneal micro-incisions calibrated for the micro-instrumentation the practitioner has decided to use. Their quality will be key for the success of the technique to prevent, in particular, undesirable leakage, the primary source of anterior chamber instability during surgery. At first, the pioneers used vitreoretinal surgery sclerotomes (Styletto 20 G), which did not prove to be appropriate. Instead, current practice prefers precalibrated knives adapted to the requirements of bimanual phaco.
There are diamond knives capable of creating highly stable 1.2 mm incisions. In my own experience I have preferred to use disposable Duet® steel blade knives to create trapezoidal incisions ranging between 1.2 and 1.4 mm or 1.4-1.6 mm with a good valve and facilitating the movement of the instruments within the incision. There is also the Clearcut SidePort® range for square 1 mm or 1.2 mm or 1.5 mm incisions, the Laser Edge® range for square 1.4 mm or trapezoidal 1.4- 1.6 mm or 1.5-1.7 mm incisions and a knife for enlarging incisions from 1.5 to 2 mm to inject ultra-thin implants.
For capsulorhexis
Only very few practitioners already master the cystotome 26 G needle capsulorhexis technique. For most surgeons wishing to transition to bimanual phaco, the capsulorhexis forceps enables perfect control of the circular and continuous cutting process of the anterior capsule by providing a good diameter while avoiding prejudicial rhexis discharge towards the equator [of the crystalline lens]. Larry Laks designed the Duet® bimanual capsulorhexis forceps which can be introduced through an incision of less than 1mm, with a short beak and a smooth introduction tip to prevent surges when being manoeuvred inside a microincision. The end of the Duet® forceps can be separated from the handle, which represents two more advantages: it is easier to clean, and exchange is less expensive in the event of breakage of the distal extremity. Other short beak forceps are available on the market, such as the Verges and Fine forceps.
For nucleofragmentation
The surgeon introduces an irrigation probe with one or two infusion openings into the anterior chamber through the incision with the left hand if he or she is right-handed, and inversely if left-handed. It is essential that the infusion flow rate be higher than the aspiration rate; the shape of this probe is optimised to ensure good flow through one or more round or oval, distal or lateral openings. There are therefore numerous models to choose from, of variable length and volume. Each practitioner should chose the instrument best adapted to his or her technique. Personally, I prefer distal to lateral infusion. The Duet® system supplies a set of several instruments to handle all situations: a two-opening irrigation probe for Divide & Conquer, and several 20 G chopper tips to be screwed onto the irrigator handle. The following distal infusion choppers provide a good irrigation flow rate, and can be introduced through an incision of 1.2 mm:
- Braga-Mele’s choppers, which are 1.5 to 2 mm long and have a 90° angle end with two lateral infusion openings, and Nagahara’s lateral cutting face and foam tip chopper to split nuclei during horizontal chop. Chang’s chopper, which is an original design with a progressive radial curve and a foam tip.
- Fine’s, Olson’s and Agarwal’s short choppers with 1 mm cutting tips for vertical chop.
Other companies also offer irrigating choppers of 19 G calibre with two lateral irrigation ports or three irrigation openings. These choppers can be introduced through an incision of 1.4 mm to be manoeuvred within the anterior chamber. Finally, there is the Cobra® infusion canula with a ladder-step end that acts as a micromanipulator and two posterior infusion openings. This probe can be introduced through a 1.5 mm incision and provides irrigation while pushing back the posterior capsule.
For Irrigation / Aspiration
Both irrigation and aspiration canulas are introduced into the anterior chamber: The aspiration canula is used under the anterior capsulorhexis canopy to aspirate the cortical matter, while the irrigation canula stabilises the anterior chamber for being filled with BSS. The Duet® 20 G I/A canulas allow for right distal infusion with an excellent flow rate, while the rough end of the aspiration canula can be used for polishing the posterior capsule. There are also smooth ovoid 20 G I/A probes, and rough-tipped disposable I/A 21 G canulas.
